This invention relates to a process and apparatus for continuously producing flat plate-type, rod-type, or shaped products from preliminarily expanded beads of polystyrene or a mixture of said beads with foamed polystyrene pieces recovered for reuse as raw materials, and more particularly to a process and apparatus for continuously producing shaped foamed articles, which comprises enveloping preliminarily expanded beads as raw materials with a circulating steam-permeable belt or belts, preferably cloth belts, passing the enveloped beads through a pressure sealing device composed of a tubular passage capable of squeezing and successively through a heating zone in pressure steam chamber at a temperature between 100.degree. and 125.degree.C, thereby softening and re-expanding the beads by steam heating, reducing an apparent volume of the enveloped re-expanded beads in a course towards another pressure sealing device at an outlet of the pressure steam chamber, thereby allowing the softened and re-expanded beads to adhere tightly one to another in a continuous foamed mass, or also additionally to a liner material if the eveloped beads are accompanied with liner material, cooling the enveloped foamed mass while maintaining a limited volume of the enveloped foamed mass, and separating the resulting shaped products of re-expanded beads from the belt by a set of rollers at the end of processing line.
The enveloped mass are generally a continuous mass in a flat plate or rod state in the processing steps. When the enveloped mass is cooled while maintaining its limited volume, and when a product having a small thickness, for example, a thickness of 10 mm or less is to be produced, a force of expanding pressure of the beads to press the belt to the outside is small, and therefore a sliding resistance is also small in the passage of the belt. Also, as cooling can be carried out rapidly, it can be effected in the atmosphere. However, when thickness of product increases from 15 mm to 100 mm, cooling is slowly carried out in proportion to the square of the thickness, and a distance required for the cooling is prolonged. The belt is more strongly pressed to the wall surface of the passage by the pressure of re-expanding and the sliding resistance of the belt sometimes exceeds the limit of strength of the belt. To carry out the cooling effectively even in said latter case, the pressure sealing device at the outlet of the pressure steam chamber is directly connected to a pressurized cooling chamber in the present invention, and the pressure of re-expanding is suppressed by applying a pressure to the cooling water or air of the cooling chamber, thereby controlling the sliding resistance of the belt to within the limit of the strength of the belt. Further, according to the present invention, a pressure sealing device is provided also at the outlet of the pressure cooling chamber to effect pressure sealing. Furthermore, according to the present invention, a plurality of flexible female molds of elastomer are provided in parallel on and along one of two cloth belts enveloping preliminarily expanded beads from upside and downside, to continuously form individually independent shaped male articles in the respective female molds.
According to the conventional, well-known process for continuously producing boards of foamed polystyrene based on pressure steam heating, preliminarily foamed beads of polystyrene are inserted between two steel belts having small steam-permeable perforations and spaced by fixed side walls of predetermined height on both edges, subjected to heat shaping by passing steam therethrough from a pressure steam chamber behind the belt surfaces, cooled as the foamed mass is in the inserted state and cut into a predetermined shape. In said well-known art, both side edge parts of the steel belts are open to the atmosphere, and the pressure steam sealing is carried out behind the belt surfaces. The belts are liable to meander in a zigzag manner. Once the belts meander in the zigzag manner, the pressure steam sealing is deteriorated, resulting in occurrence of much steam leakage. The present invention is distinguished from the prior art in the sealing mechanism. In the prior art, the processing is carried out while holding the beads inserted between the belts at a constant distance throughout all the steps of heating and cooling, whereas in the present invention the thickness of the beads within the tubular passage of pressure sealing devices at the inlet and outlet of the pressure processing chambers as well as the distance of two belts within the pressure steam chamber and the pressure cooling chamber are not always constant. In the present invention, thickness of the foamed beds sandwiched between the two belts namely the distance of the two belts passing through each part of processing is adjusted, unless the thickness and density of the final shaped product are adversely influenced thereby, mainly to make a tension on the cloth belts as small as possible and reduce the sliding resistance of the cloth belts. Therefore, the present invention is also distinguished from the prior art in changing the distance of two belts from one step to another. Furthermore, the use of pressure water in cooling in the present invention considerably increases the shaping speed, and the provision of a plurality of female molds in parallel and in series on and along one of the belts ensures a continuous production of individually independent shaped articles, and the use of flexible cloth belts is also characteristic of the present invention.
When warped yarns arranged in parallel, or rough non-woven fabrics of particularly a mesh of small numbers, made from split fiber webs, parallel yarns, parallel tapes, laid one upon another cross-wise, are used as a liner material together with the preliminary expanded beads, the heated and re-expanded beads are laminated on the liner material so as to enclose the fibers, yarns or tapes of the liner materials into a skin part of the foamed products, and a tight adhesion of the foamed mass to the liner is much improved thereby. Liner materials such as paper, film, etc. have not a good steam permeability, and particularly paper is weak against water, and thus laminated onto one side or both sides of products after the shaping in the heretofore well known manner.
The present invention will be described in detail by way of the accompanying drawings.